To address the computational complexity of accurately calculating molecular absorption spectra in high-temperature environments and meet the demand for theoretical absorption spectrum calculations in broad-spectrum measurement fields, this study developed a precise and fast calculation model for molecular absorption spectra based on the High-Temperature molecular spectroscopic absorption parameters database (HITEMP). The model was implemented using Python language, employing a line-by-line calculation approach combined with simplification of line shape functions, line wing truncation criteria, and optimization of spectral line databases. The Hartmann-Tran line shape function was used as the standard absorption spectrum line shape, and partially-Correlated quadratic-Speed-Dependent Hard-Collision Profile (pCqSDHC) was developed for relevant second-order velocity-dependent hard-collision functions. By incorporating the Complex Probability Function (CPF) and simplifying the model, the line shape functions were calculated accurately and rapidly, resulting in a 20-fold increase in computational speed compared to theoretical models. The line wing truncation criteria were determined based on the spectral calculation residual at the level of 10-5 and involved the truncation of fixed wavenumbers combined with equal multiple truncations of spectral line half widths. Spectral data for each temperature gradient of 100 K were selected using a threshold line intensity of 10-25?cm-1/(mol?cm-2) and integrated to create an optimized database. The absorption spectra of water molecules were calculated within the range of 6 500 ~ 8 000 cm-1 and compared with the simulation results from "SpectraPlot.com", a molecular gas integrated spectral modeling website. The calculation error of the line-by-line model was at the level of 10-7, while the optimized model achieved a calculation error at the level of 10-5, with an average speed improvement of 25 times. This model enables efficient and accurate calculation of theoretical absorption spectra for absorption spectral measurements and provides a theoretical foundation for measuring studies based on wide-tunable and supercontinuum laser absorption spectra in complex environments.